1. Field of the Invention
The invention concerns a sensor arrangement for a coating system according to the preamble of Claim 1 and also a coating system with such a sensor arrangement.
2. Relevant Prior Art
In modem painting systems, known rotary atomizers are used for which a so-called bell-shaped plate is driven by a compressed-air turbine at high rpm. The bell-shaped plate usually has the form of a truncated cone and expands in the spray direction, with the coating agent to be applied being accelerated in the axial direction and especially in the radial direction in the truncated cone-like bell-shaped plate due to centrifugal forces, so that a conical spray stream is produced at the outer edge of the bell-shaped plate.
From DE 43 06 800 A1, it is further known to measure the rpm of the compressed-air turbine. Here, reflective markings are applied onto the turbine wheel of the compressed-air turbine. These markings rotate with the turbine wheel and are detected by a stationary optical sensor by means of optical fibers. For achieving good painting results, the rotary atomizer with the compressed-air turbine is set to a high voltage, while the workpieces to be painted and the optical sensor are electrically grounded.
The use of flexible optical fibers for detecting the optical markings on the turbine wheel enables a stationary arrangement of the optical sensor and potential isolation of the sensor relative to the high voltage of the rotary atomizer.
A disadvantage of this known sensor arrangement with optical fibers is first the fact that for converting the optical signals transmitted in the optical fibers into an electrical signal, a relatively large number of optoelectrical converters is required.
Secondly, for an optical fiber connection, only a relatively small number of separation points is possible, because transmission losses occur at each separation point. For increasing component modularity of modem coating systems, with a corresponding increase in the number of separation points, the known optical fiber technology thus runs into its limitations.
Furthermore, optical fibers are relatively sensitive to breaks, which can lead to operational failure of the rpm measurement system for an excess mechanical load on the sensor arrangement.
The invention is thus based on the problem of improving the previously described known sensor arrangement to the effect that greater component modularity is possible. The mechanical load capacity should be as large as possible.